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Rates equilibrium Hess' Law

Total questions: 27

Worksheet time: 26mins

Name
Class
Date
1.

Using the equations below:


C(s) + O2(g) → CO2(g) ∆H = –390 kJ

Mn(s) + O2(g) → MnO2(s) ∆H = –520 kJ


what is ∆H (in kJ) for the following reaction?


MnO2(s) + C(s) → Mn(s) + CO2(g)

a)

910

b)

130

c)

-130

d)

-910

2.

For Hess' Law to be used what must be the same for all of the reactions being studied?

a)

The initial conditions of pressure and temperature.

b)

The final conditions of pressure and temperature.

c)

The initial and the final conditions of pressure and temperature.

d)

The initial and the final conditions of pressure and temperature, and the number of moles of reactants.

3.

Which of the following statements are true for the reaction:


SO2(g) + 1/2O2(g) ↔ SO3(g) ΔH = –92 kJ mol-1


Where ↔ indicates that the reaction can proceed in the forward and the reverse direction.

a)

The forward and reverse reaction both produce 92 kJ of energy.

b)

Oxidising 2 moles of SO2 would produce twice as much energy.

c)

The reverse reaction has an enthalpy of +92 kJ mol-1.

d)

Collecting the SO3 produced in the liquid state would not change the measured enthalpy.

4.

In order to find the enthalpy of combustion of C3H8 how must the enthalpy changes be arranged?

a)

ΔH3 = ΔH1 + ΔH2

b)

ΔH2 = ΔH3 - ΔH1

c)

ΔH1 = ΔH2 - ΔH3

d)

0 = ΔH1 + ΔH2 + ΔH3

5.

Standard conditions are defined as...

a)

298K and 1.00 x 105 kPa

b)

273K and 1.00 x 105 kPa

6.
A chemical reaction that requires energy is a
a)
exothermic reaction 
b)
endothermic reaction 
c)
over reaction 
d)
redox reaction
7.
The enthalpies of combustion of C(s), H2(g) and C4H9OH(l) (in kJmol-1) are as follows  
C(s) + O2(g)   ->  CO2(g)                                               ∆H=a
H2(g) + ½O2(g)   ->   H2O(l)                                        ∆H=b
C4H9OH(l) + 6O2(g)   ->   4CO2(g) + 5H2O(l)  ∆H=c
What is the enthalpy change for the reaction shown below?
  4C(g) + 5H2(l) + ½O2(g)   ->   C4H9OH(l)
a)
c – 4a – 5b
b)
2a + 10b - c
c)
4a + 5b - c
d)
2a + 5b + c
8.
The enthalpy change for the reaction
C(s, graphite) + 1⁄2O2(g) --> CO(g) cannot be measured directly since some carbon dioxide is always formed in the reaction.
It can be calculated using Hess’s Law and the enthalpy changes of combustion of graphite and of carbon monoxide.
C(s, graphite) + O2(g) --> CO2    ΔH=-394 kJmol–1
CO(g) + 1⁄2O2(g) --> CO2  ΔH=-283 kJmol–1  
The enthalpy change for the reaction of graphite with oxygen to give carbon monoxide is 
a)
-677 kJmol–1 
b)
+111 kJmol–1 
c)
-111 kJmol–1 
d)
+677 kJmol–1 
9.

How much energy is associated with the process of creating 4 mol NO2

a)

1933 kJ

b)

-1875 kJ

c)

3866 kJ

d)

-3750 kJ

10.
A reaction is performed in a beaker with a temperature probe recording the temperature changes of the reaction.  If the temperature began at 15.0 degrees Celsius and ended at 27.5 degrees Celsius.  If the reaction is our system, is the system endothermic or exothermic?
a)
Exothermic
b)
Endothermic
11.
In an exothermic reaction, heat is ...
a)
taken in
b)
given out
c)
nothing happens
d)
it gets colder
12.
Baking bread and cooking an egg are examples of....?
a)
Endothermic processes
b)
Exothermic processess
c)
Combustion
d)
Yummy!
13.
When you freeze water, it turns to ice.  What process is this?
a)
 Exothermic
b)
Endothermic
c)
Condensing
d)
Melting
14.
If a chemical reaction is EXOTHERMIC, the temperature would....
a)
Stay the same
b)
Increase
c)
Decrease
d)
Be negative
15.

The following equations show the oxidation of carbon and carbon monoxide to carbon dioxide.


C(s) +O2(g) → CO2(g) ΔH = –x kJ mol–1

CO(g) + O2(g) → CO2(g) ΔH = –y kJ mol–1


What is the enthalpy change, in kJ mol–1, for the oxidation of carbon to carbon monoxide?


C(s) + O2(g) → CO(g)

a)

x + y

b)

-x - y

c)

y - x

d)

x - y

16.
What are the two factors to look for when determining if the reaction is at equilibrium?
a)
Forward reaction rate is faster than the reverse and concentrations are equal
b)
Forward and reverse reaction rates are equal and concentration is conctant
c)
Forward and revers reaction rates are equal and concentration is equal
d)
Forward reaction rate is faster than the reverse and concentration is equal
17.

Identify the incorrect statement about achieving equilibrium.

a)

achieved when product and reactant concentrations are equal

b)

achieved when forward and reverse reaction rates are same

c)

achieved when concentration of reactants is stable/constant

d)

achieved when concentration ratio of reactants to products becomes stable, thus fixing the equilibrium constant (equilibrium position)

18.
At what time the reaction reached equilibrium?
a)
t1
b)
t2
c)
t3
d)
t4
19.
Identify the labels (a) and (b) on the graph.
a)
a is concentration of reactants and b is the concentration of product
b)
a is concentration of product and b is the concentration of reactant
c)
a is the volume of reactants and b is the volume of product
d)
a the mass of reactants and b is the mass of product
20.
Define chemical equilibrium.
a)
A reaction is reversible.
b)
The concentration of the reactants is equal to the concentration of the products.
c)
The rate of a forward reaction is equal to the rate of the reverse reaction.
d)
The reaction stops and no further change in concentration occurs.
21.

Catalysts permit reactions to proceed along a ___________energy path.

a)

lower

b)

higher

c)

magnetic

d)

psycho's

22.
Hydrochloric acid can react with sodium thiosulfate solution to form a sulfur precipitate. The equation is:
Na2S2O3(aq) + 2HCl(aq) → 2S(s) + SO2(g) + 2NaCl(aq) + H2O(l)
Which list below contains only changes that will decrease the rate of this reaction?
a)
Increase the temperature, increase the hydrochloric acid concentration and add a catalyst
b)
Decrease the temperature and add a catalyst
c)
Decrease in temperature, decrease in concentration of the hydrochloric acid, addition of water to the sodium thiosulfate
d)
Decrease the concentration of the sodium thiosulfate solution and increase the temperature
23.

The Maxwell–Boltzmann distribution of molecular energies in a sample of gas at a fixed temperature is shown.


Which letter represents the mean energy of the molecules?

a)

A

b)

B

c)

C

d)

D

24.

The diagram shows the Maxwell−Boltzmann distribution of molecular energies in a gas at two different temperatures.


Which letter represents the most probable energy of the molecules at the higher temperature?

a)

A

b)

B

c)

C

d)

D

25.

The question below is about the Maxwell–Boltzmann distribution shown for a sample of a gas, X, at two different temperatures.


Which statement is correct for the higher temperature?

a)

The area under the curve to the left of Ea decreases.

b)

The total area under the curve increases.

c)

The activation energy decreases.

d)

More molecules have the mean energy.

26.

The graph below shows a typical energy distribution for particles of an ideal gas in a sealed container at a fixed temperature.


Which of the following statements is true?

a)

Position A represents the mean energy of a molecule in the container.

b)

Addition of a catalyst moves the position of EA to the right.

c)

The area under the curve to the right of EA represents the number of molecules with enough energy to react.

d)

The position of the peak of the curve at a higher temperature is further away from both axes.

27.

The total area under the distribution curve represents

a)

total energy.

b)

activation energy.

c)

total number of reacting molecules.

d)

total number of molecules present.

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